1. Field of the Invention
The present invention relates to a process and an apparatus for determining, through presumption, pressure losses of exhaust gas purification honeycomb structural bodies such as diesel particulate filters (DPF) to be used for the purification of exhaust gases from diesel engines at points of time when the exhaust gas purification honeycomb structural bodies are to be regenerated.
2. Related Art Statement
The above DPF is a honeycomb structural body made of a porous ceramic and having through holes alternatively sealed at opposite end faces, and the honeycomb structural body is assembled into an exhaust line of a diesel engine so that exhaust gases may be fed into the honeycomb structural body from one end face, and flown to the other end face through partition walls between the through holes. Fine particles (particulates) contained in the exhaust gas are filtered off with the partition walls made of the porous ceramic.
In such an exhaust gas purification honeycomb structural body, as the particulates contained in the exhaust gas are heaped on the filter, the pressure loss of the filter becomes extremely great. When the filter heaped with a large amount of the particulates is used as it is, performance of the engine is deteriorated. Accordingly, it is necessary to burn out the particulates heaped on the filter, that is, to regenerate the honeycomb structural body at a point of time when an amount of the heaped particulates reaches a given level. However, since the weight of the particulates heaped on the filter cannot be directly measured after the honeycomb structural body is mounted on the diesel engine or the like, the honeycomb structural body starts to be regenerated at such a timing when the pressure loss of the filter as measured reaches a given level.
However, the pressure loss of the filter generally has a low correlationship to the amount of the particulates heaped on the filter. Even when the pressure loss reaches a given level, an amount of the particulates heaped is actually smaller in some cases than expected, so that no combustion occurs. To the contrary, in the case that an amount of the particulates heaped on the filter is too large at a point of time when the pressure loss reaches a given level, a great amount of heat is generated through the combustion of the heaped particulates, which may crack or melt the filter in other cases.
Therefore, it is necessary to detect the pressure loss at a point of time when the particulates such as soot are caught in an amount for the filter to be suitably regenerated, with respect to the respective filters. However, in order to determine the pressure loss of each honeycomb structural body at a point of time when the regeneration is to be started, it is necessary that a particulate-containing gas is flown through the honeycomb structural body to deposit the particulates thereon, and continuously flown through the honeycomb structural body until the amount of the caught particulates reaches such a level that the honeycomb structural body needs to start to be regenerated, and that the pressure loss is finally measured at a point of time when the amount of the caught particulates reaches such a level. Therefore, the above process unfavorably necessitates a large inspection time.